Coating composition comprising submicron calcium carbonate and use thereof

ABSTRACT

Coating composition providing gloss and opacity on application, having a pigment volume concentration of from 5% up to the critical pigment volume concentration and characterised in that comprises at least one ground natural calcium carbonate having a volume median diameter of between 0.05 and 0.3 μm, and at least one pigment having a refractive index of greater than or equal to 2.5.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. application Ser. No. 13/522,768, filed Sep.7, 2012, which is a U.S. national phase of PCT Application No.PCT/EP2011/050953, filed Jan. 25, 2011, which claims priority toEuropean Application No. 10151721.7, filed Jan. 26, 2010 and U.S.Provisional Application No. 61/400,648, filed Jul. 30, 2010, theentirety of which are hereby incorporated by reference.

The present invention relates to glossing and opacifying coatingcompositions comprising submicron natural ground calcium carbonate. Theinvention further relates to a process to prepare a glossing andopacifying coating composition implementing submicron natural groundcalcium carbonate, and to the use of submicron natural ground calciumcarbonate in glossing and opacifying coating compositions.

Mineral pigments are widely used in coating systems, not only todecrease formulation costs but further to improve certain properties ofthe coating formulation, during its preparation or storage, or during orfollowing its application to a substrate. In the realm of paintformulations, coating systems almost invariably implement titaniumdioxide.

In the context of paint applications, pigments with a refraction indexof at least 2.5 are highly appreciated. One especially preferred pigmentin this respect is titanium dioxide (TiO₂), particularly when of therutile form having a refractive index of 2.7 (Light Scattering byPigmentary Rutile in Polymeric Films, Richard A. Slepetys, William F.Sullivan Ind. Eng. Chem. Prod. Res. Dev., 1970, 9 (3), pp 266-271) forproviding significant opacity or hiding power. Titanium dioxide pigmentsmarketed for use in paint formulation are well known to present a narrowparticle size distribution along with a median particle diameter ofbetween 0.2 and 0.6 μm, depending on the material and the mean particlesize measurement method. Zinc sulphide and zinc oxide are similarlyemployed.

Titanium dioxide suffers however from being relatively high in cost,resulting in a continued desire to find lower-cost TiO₂ partialreplacement pigments that do not translate in a reduction of optical andother coating composition properties.

GB1404564 describes ultrafine natural calcium carbonate filled paintsand pigments, wherein said natural calcium carbonate has a particlediameter of from 0.5 to 4 μm and is employed to partially replacetitanium dioxide. In this vein, Polcarb™ (commercialized by the companyImerys) is said to be suitable for glossing paint formulations, whichhas a mean particle size of 0.9 μm. However, such natural calciumcarbonate products do not allow the replacement of a part of TiO₂ inglossing paint formulation having a pigment volume concentration belowthe critical pigment volume concentration, without loss of gloss oropacity.

For the purpose of the present invention, the pigment volumeconcentration (PVC) is understood to refer to the fraction, quoted in %of pigment volume relative to the total volume of the pigment plus theother components of the formulation, i.e. it accounts for the pigmentvolume relative to the total formulation volume in the final (dried;i.e. excluding water or other solvent) coating.

The critical pigment volume concentration (CPVC) is defined as thepigment volume concentration as of which, if exceeded, the resincomponent of the coating formulation is no longer sufficient to entirelycoat all of the pigment particles in a coating. It is well known thatabove the CPVC, formulations generally provide a matt finish. Bycontrast, glossy paint formulations implement a PVC that is below theCPVC.

U.S. Pat. No. 5,171,631 discloses a coating composition for developinghiding on a suitable substrate, the coating composition having a pigmentvolume concentration (PVC) up to a critical pigment volume concentration(CPVC) and a pigment system comprising about 70-98% by volume oftitanium dioxide and about 2-30% by volume of an aluminium trihydrate(ATH) spacer/extender pigment having a medium particle size of about 0.2microns. FIG. 1 of U.S. Pat. No. 5,171,631 shows a d₉₈/d₅₀ ratio valueof approximately 2.7, which corresponds to a relatively narrow particlesize distribution. Although it is stated that, provided this ATH has amedian particle size and particle size distribution generally similar tothe median particle size and particle size distribution curve of TiO₂, aportion of TiO₂ may be replaced with an equal volume of ATH with no lossof hiding, FIG. 2 of U.S. Pat. No. 5,171,631 shows that theATH-TiO₂-comprising paint formulations generally fail to achieve thesame opacity values as the control paint formulation comprising TiO₂alone.

Natural ground calcium carbonate (GCC), as opposed to its syntheticcounterpart, precipitated calcium carbonate (PCC), generally suffers inthis application field from a broad particle size distribution andirregular particle shapes. Indeed, as natural ground calcium carbonateis prepared by the grinding down of mined calcite, marble, chalk orlimestone-containing stones, it is difficult to ensure that these stonesare ultimately fractioned to form fine particles having a very uniformparticle size.

By contrast, PCC is formed by a process of building crystals aroundnucleation sites. Control of nucleation and particle size development,particularly in the size domain under a few micrometers, during PCCprecipitation, has, over the years, become a well studied science, andPCC particles having small and very uniform particle sizes and shapesare now widely available. As in U.S. Pat. No. 5,171,631, the advantagesof employing a uniform particle size product as a titanium dioxidespacer are known. In this domain, Specialty Minerals advertises AlbafilPCC, a fine, 0.7 micron prismatic calcite, and a range of ultrafine ornano PCCs, namely Calofort S PCC, Calofort U PCC, Ultra-Pflex PCC andMuitifex MM PCC, each having a median diameter of 0.07 micron, statingthat precipitated calcium carbonate (PCC) is most commonly used in paintas an extender for titanium dioxide TiO₂. The small and narrowlydistributed PCC particles help space the individual TiO₇ particles andmaximize their hiding power.

In view of the above teachings of the prior art, it was remarkable thatthe Applicant found that a ground natural calcium carbonate that isfiner than ground natural calcium carbonate products previously offeredin this domain, may be used as a replacement or complementary pigmentfor pigments with a refraction index of at least 2.5, especially TiO₂,even in the case when this ground natural calcium carbonate features arelatively broad particle size distribution and/or a median diameterthat is different from that of the pigment to be replaced. By contrastto the results of U.S. Pat. No. 5,171,631 achieved with ATH, the groundnatural calcium carbonate employed in the present invention not onlymore fully maintains the gloss and opacity of the paint formulation whenused to replace part of the formulation pigment such as TiO₂ at constantPVC, it may even lead to a gloss and/or opacity improvement.

A first object of the present invention is accordingly a coatingcomposition having the same or even improved gloss and opacity as acoating composition of pigments with a refraction index of at least 2.5,but wherein the content of this pigment is reduced at the same PVC.

The solution of this problem according to the present invention is acoating composition having a pigment volume concentration (PVC) of from5 vol.-% up to the critical pigment volume concentration (CPVC), whichcomprises at least one ground natural calcium carbonate having a volumemedian diameter d₅₀ of between 0.05 and 0.3 μm, (hereafter submicronground natural calcium carbonate, SMGCC), and at least one pigmenthaving a refractive index of greater than or equal to 2.5.

For the purpose of the present application, CPVC is determined accordingto the measurement method given in the examples section herebelow.

For the purpose of the present invention, the volume median diameter d₅₀(d₅₀ (Mal)) and the d₉₈ (d₉₈ (Mal)) are measured according to theMalvern measurement method provided in the examples section herebelow.

In this respect, the d₅₀ and d₉₈ values define the diameters, at which50 vol.-% of the particles measured have a diameter smaller than thed₅₀, and at which 98 vol.-% of the particles measured have a diametersmaller than the d₉₈ value, respectively.

Preferably, the coating composition has a PVC of from 10 to 30 vol.-%,more preferably 15 to 25 vol.-%, even more preferably 17 to 21 vol.-%,e.g. 19 vol.-%.

Preferably, said SMGCC has a volume median diameter d₅₀ of between 0.08and 0.3 μm, preferably of between 0.1 and 0.2 μm, e.g. 0.15 μm.

Thus, according to the present invention, it is not only preferred touse submicron particles, but it is even possibly and advantageous to useSMGCC particles having a volume median diameter d₅₀ in the low nanometerrange.

In one embodiment, said SMGCC has a d₉₈/d₅₀ of greater than 3. Asindicated above and in contrast to the prior art, this ground naturalcalcium carbonate may, in an optional embodiment, have a particle sizedistribution that is broad and dissimilar to the particle sizedistribution of said pigment having a refractive index of greater thanor equal to 2.5 employed in the composition. Indeed, even a bi- ormultimodal SMGCC particle size distribution may be envisioned.

As shown in the examples section herebelow, it is not necessary thatsaid SMGCC have a volume median diameter d₅₀ that is equivalent to thevolume median diameter d₅₀ of said pigment having a refractive index ofgreater than or equal to 2.5, though this embodiment is not excludedfrom the present invention. The volume median diameter d₅₀ of SMGCC maydiffer from the volume median diameter d₅₀ of said pigment having arefractive index of greater than or equal to 2.5 by up to approximately0.4 μm, preferably up to 0.3 μm, especially up to 0.2 μm.

Furthermore, as shown by the examples section herebelow, said SMGCC mayfeature a broad and even non-uniform particle size distribution relativeto the distribution of said pigment having a refractive index of greaterthan or equal to 2.5 is, though again this does not exclude the casewhere the particle size distributions of SMGCC and said pigment having arefractive index of greater than or equal to 2.5 is are similar inbreadth.

In a preferred embodiment, said SMGCC has a d₉₈ of less than or equal to1 μm, more preferably of less than or equal to 0.8 μm, even morepreferably of less than or equal to 0.6 μm, e.g. 0.5 μm and even morepreferably of less than or equal to 0.4 μm, e.g. 0.3 μm.

Preferably, said SMGCC has a refraction index of approximately 1.4 to1.8, more preferably of about 1.5 to 1.7, e.g. 1.6.

In another preferred embodiment, said pigment having a refractive indexof greater than or equal to 2.5 is selected from one or more of thegroup comprising titanium dioxide, zinc sulphide and zinc oxide. In amore preferred embodiment, said pigment having a refractive index ofgreater than or equal to 2.5 is titanium dioxide.

If the pigment having a refractive index of greater than or equal to 2.5is titanium dioxide, it is preferred that the titanium dioxide:SMGCCweight ratio is of 70:30 to 98:2, and it is even more preferred that thetitanium dioxide:SMGCC weight ratio is of 75:25 to 90:10, mostpreferably the titanium dioxide:SMGCC weight ratio is of 80:20 to 85:15,e.g. 88:12.

In an alternative embodiment, the coating composition according to thepresent invention further comprises one or more materials selected fromthe group comprising clay, talc, magnesium carbonate, precipitatedcalcium carbonate (PCC), barium sulphate, mica and bentonite. In thecase where magnesium carbonate is implemented in combination with SMGCC,this may be in the form of a dolomite.

It is an especially preferred embodiment of the invention that the glossand/or opacity of the coating composition according to the invention isequal to or greater than the gloss and/or opacity of the samecomposition implementing the same amount of said pigment having arefractive index of greater than or equal to 2.5 in place of said groundnatural calcium carbonate having a d₅₀ of between 0.05 and 0.3 μm.

For the purpose of the present invention, the gloss of a coatingcomposition applied to a substrate is measured according to themeasurement method provided in the examples section herebelow.

For the purpose of the present invention, the opacity of a coatingcomposition applied to a substrate is measured according to themeasurement method provided in the examples section herebelow.

In an especially preferred embodiment the coating composition of thepresent invention is characterised in that the gloss of the compositionis within a range of ±10% of the gloss of a composition wherein theSMGCC is fully replaced by said pigment having a refractive index ofgreater than or equal to 2.5 at a constant PVC value in the range offrom 5 vol.-% up to the CPVC.

Preferably, the gloss of the coating composition according to thepresent invention is within a range of ±5%, and more preferably within arange of ±3%, of the gloss of a composition wherein the SMGCC is fullyreplaced by said pigment having a refractive index of greater than orequal to 2.5.

It is especially preferred that the gloss of the coating composition isincreased by at least 1% relative to the gloss of a composition whereinthe SMGCC is fully replaced by said pigment having a refractive index ofgreater than or equal to 2.5. Relative to this embodiment, the gloss ofthe coating composition of the present invention is preferably increasedby at least 5% relative to the gloss of the composition wherein theSMGCC is fully replaced by said pigment having a refractive index ofgreater than or equal to 2.5.

In a preferred embodiment, said SMGCC is dispersed with one or moredispersants. Conventional dispersants known to the skilled person can beused. The dispersant can be anionic, cationic or non-ionic. A preferreddispersant is based on polyacrylic acid.

Said coating composition may be applied to a variety of substrates,including but not limited to concrete, wood, paper, metal and board.

In a preferred embodiment, said coating composition is applied to asubstrate in an amount so as to form a layer having a thickness ofbetween 40 and 400 μm, preferably of between 100 to 350 μm, morepreferably of between 150 to 300 μm, e.g. between 200 and 250 μm.

Following application to a substrate, said coating compositionpreferably provides a gloss measured at 60° according to DIN 67 530 ofat least 70%, more preferably of at least 75%, especially at least 80%.

Following application to a substrate, said coating compositionpreferably provides an opacity (contrast ratio) determined according toISO 6504/3 of at least 95%, more preferably at least 97%, especially atleast 98%.

Said coating composition may further include one or more componentsselected from the group comprising; resins, such as latex oracrylate-based binders, preferably in the form of an aqueous emulsion;pigments, such as titanium dioxide; additives, such as defoamers,levelling agents, flatting agents, preservatives, optical brighteners,light stabilizers and rheological additives, such as thickeners,dispersants; solvents, such as glycol ethers and fillers, such ashollow-sphere polymeric pigments (Ropaque™).

Generally, any additives, which can usually used in water basedcoatings, which are well-known in the art may be used in the presentinvention. Such additives include, but are not limited to binders, suchas latex, which may be based on pure acrylic compounds, styrene acryliccompounds, vinyl acrylic compounds, styrene butadiene, ethylene vinylacetate, vinyl acetate, poly vinyl acetate, starch polymers, etc.;alkyds, e.g. of the water reducible and emulsified types, such as soyaoil, tall oil, which may be silicone modified, polyurethane modified,etc.; polyurethanes, which may be both solvent containing or solventfree.

Further additives include titanium dioxide (rutile or anatase), andcommon pigments and/or fillers such as zinc oxide, nephelene syenite,diatomaceous earth, aluminum silicates, calcined clays, ball clays,water washed clays, barium sulphate, magnesium silicate, quartz, mica,and wollastonite, as well as colored inorganic and organic pigments.

Further additives, which may be useful in the present invention includesolvents such as aromatic and aliphatic hydrocarbons, mineral spirits,naphtha, propylene and ethylene glycols, etc.; coalescing solvents suchas texanol, butyl carbitol, butyl diglycol, butyl cellosolve, diethyleneglycol mono methyl/butyl/hexyl/ethyl ethers, etc.; plasticizers such asvarious phthalates, such as dibutyl, diethyl, dioctyl, dimethyl, benzyl,dialkyl phthalates, etc.; anti settling agents, such as attapulgiteclay, cellulosic thickeners (e.g. HEC, HMEC, HMPC, etc); dispersants,such as polyacrylates, which may be sodium, ammonium, and/or potassiumneutralized, and/or hydrophobically modified; surfactants such asanionic or non-ionic surfactants; rheology modifiers such as associativeand non-associative acrylics, and polyurethanes; defoamers, which may bemineral oil based, silicone based, etc.; biocides, e.g. those commonlyused for in can preservation; mildewcides, e.g. those commonly used forresistance to mildew of dried paints; driers, especially those typicallyused with emulsified alkyds/water reducible alkyds; a wide variety ofmetals such as cobalt, zinc, zirconium, calcium, manganese, etc.;UV-absorbers, such as those typically used in either UV cure systems, orin some wood stains and finishes; stabilizers such as hindered aminelight stabilizers, e.g. those typically used in either UV cure systems,or in some wood stains and finishes in combination with UV absorbers.

Further additives, which may be used in the present invention are anyone commonly used in coating and paint formulations, and can be found incorresponding textbooks, and guidelines known to the person skilled inthe art such as the VdL-Richtlinie “Bautenanstrichstoffe” (VdL-RL01/Juni 2004; published by Verband der deutschen Lackindustrie e.V.).

Preferably, the coating composition has a Brookfield viscosity of from200 to 500 mPa·s, more preferably of from 250 to 400 mPa·s, e.g. 300mPa·s, as measured according to the measurement method provided in theexamples section herebelow.

A further object of the present invention resides in a process toprepare a coating composition according to the invention.

Accordingly the present invention also relates to a process to prepare acoating composition having a PVC of from 5 vol.-% up to the CPVC, whichis characterised by the following steps:

a) at least one ground natural calcium carbonate (SMGCC) having a volumemedian particle diameter d₅₀ of between 0.05 and 0.3 μm is provided;

b) at least one pigment having a refractive index of greater than orequal to 2.5 is provided;

c) said SMGCC of step a) is mixed with said pigment of step b).

Said SMGCC of step a) may be provided in the form of an aqueoussuspension, an aqueous dispersion or dry powder. In a preferredembodiment, said SMGCC of step a) is provided in the form of an aqueoussuspension or dispersion.

Furthermore, it is preferred that, additionally, at least one resin isprovided, which is mixed with said SMGCC of step a) and said pigment ofstep b).

Said resin is preferably a latex and/or acrylate-based binder, saidacrylate-based binder preferably being in the form of an aqueousemulsion.

Furthermore, a third object of the present invention lies in the use ofat least one ground natural calcium carbonate having a volume medianparticle diameter d₅₀ of between 0.05 and 0.3 μm, in a coatingcomposition having a PVC in the range of from 5 vol.-% up to the CPVCcomprising at least one pigment having a refractive index of greaterthan or equal to 2.5.

In this respect, it is preferred that the gloss and/or opacity of thecomposition of the present invention is equal to or greater than thegloss and/or opacity of a composition wherein the SMGCC is fullyreplaced by said pigment having a refractive index of greater than orequal to 2.5.

Another object of the present invention is a paint comprising thecoating composition of the invention.

EXAMPLES Suspension or Dispersion Solids Content (% Equivalent DryWeight)

The weight of the solid material in a suspension or dispersion isdetermined by weighing the solid material obtained by evaporating theaqueous phase of suspension and drying the obtained material to aconstant weight.

Particle Size Distribution (Volume % Particles with a Diameter <x),Volume Median Grain Diameter d₅₀, and d₉₈ (Diameter at which 98 Vol.-%of the Particles are Finer than d₉₈) of Particulate Material.

Volume median grain diameter d₅₀ was evaluated using a MalvernMastersizer 2000 (Fraunhofer). The d₉₈ value, measured using a MalvernMastersizer 2000 (Fraunhofer), indicates a diameter value such that 98%by volume of the particles have a diameter of less than this value.

BET Specific Surface Area (m²/g)

BET specific surface area values were determined using nitrogen and theBET method according to ISO 9277.

Gloss of a Coated Surface

Gloss values are measured at the listed angles according to DIN 67 530on painted surfaces prepared with a coater gap of 150 and 300 μm oncontrast cards.

Contrast Ratio (Opacity) of a Coated Surface

Contrast ratio values are determined according to ISO 6504/3 at aspreading rate of 7.5 m²/l.

Suspension or Dispersion Brookfield-Viscosity (mPas)

Brookfield-viscosities are measured with a Brookfield DV-II Viscometerequipped with a LV-3 spindle at a rotation rate of 100 rpm and roomtemperature (20±3° C.).

Pigment Volume Concentration (PVC, %)

The pigment volume concentration is calculated as described in Section6.2.3 of the book entitled “Fuellstoff” by Detlef Gysau (Hannover:Vincentz Network 2005).

$\frac{\begin{matrix}{{{Total}\mspace{14mu}{sum}\mspace{14mu}{by}\mspace{14mu}{volume}\mspace{14mu}{of}\mspace{14mu}{all}\mspace{14mu}{pigments}} +} \\{{extenders}\mspace{14mu}{in}\mspace{14mu}{paint} \times 100\%}\end{matrix}}{{Total}\mspace{14mu}{sum}\mspace{14mu}{by}\mspace{14mu}{volume}\mspace{14mu}{of}\mspace{14mu}{all}\mspace{14mu}{solid}\mspace{14mu}{ingredients}\mspace{14mu}{in}\mspace{14mu}{paint}}$

Critical Pigment Volume Concentration (CPVC, %)

The critical pigment volume concentration is a well known concentrationwidely used in the paint industry. CPVC in traditional coatings isconsidered to be the volume of pigment in relation to binder at whichthere is just enough binder to wet the pigment and at which the mixtheoretically exhibits zero porosity (cf. e.g. “Estimation of CriticalPigment Volume Concentration in Latex Paint Systems Using GasPermeation, Manouchehr Khorassani, Saeed Pourmandian, FaramarzAfshar-Taromi, and Amir Nourhani, Iranian Polymer Journal 14 (11), 2005,1000-1007). The CPVC and its measurement method according to ISO 4618are discussed in Section 6.2.4 of the book entitled “Fuellstoff” byDetlef Gysau (Hannover: Vincentz Network 2005).

Materials

SMGCC

SMGCC dispersions used in the following examples are natural groundcalcium carbonate (marble from Vermont) having the volume medianparticle size d₅₀ and particle size characteristics given in the tablebelow.

Solids SSA vol.-% d₉₈ d₅₀ SMGCC (wt-%) (m²/g) <1 μm vol.-% <0.5 μmvol.-% <0.2 μm (μm) (μm) d₉₈/d₅₀ 1 60 36.0 98.3 94.3 65.1 0.53 0.120 5.02 49 37.7 98.3 94.8 65.7 0.55 0.122 4.5 3 46 38.6 97.7 94.8 69.5 0.310.128 2.4

Titanium Dioxide

The titanium dioxide employed in the examples herebelow consists of 95%by weight of pure rutile TiO₂, with the remaining weight being accountedfor in a surface treatment of alumina, zirconia and an organic surfacetreatment agent. This pigment features a volume median diameter d₅₀ ofapproximately 0.55 μm and a d₉₈/d₅₀ (Mal) of 1.98, and is provided inthe form of an aqueous paste having a 75 wt-% solids content. Byscanning electron microscope imaging, the particles appear to be in therange of 0.2 to 0.25 μm. The refractive index of TiO₂ is 2.7.

Example 1

The following example illustrates a comparative paint composition andpaint compositions according to the invention. The formulated paintswere applied to a contrast card in the necessary amounts in order tomeasure both gloss and opacity.

Example 1 2 3 4 Comparison (CO)/Invention (IN) CO IN IN IN Paintcomposition formulation Water (g) 134 120 111 108 Hydrophilic copolymerdispersant, 50 wt-% 6.4 6.5 6.5 6.5 solids content (g) Ammonia, 24 wt-%(g) 4 4 4 4 Paraffin-based mineral oil mixture containing 7 7 7 7silicone (g) Rheotech 2000 thickener from Coatex (g) 15 15 15 15Propylene glycol (g) 10 10 10 10 Butyl diglycol (g) 5 5 5 5 DipropyleneGlycol n-Butyl Ether (g) 10 10 10 10 Ester alcohol with Mw = 216 g/mol(g) 9 9 9 9 Acrylate binder emulsion, 48 wt-% active 550 557 557 557content (g) TiO₂ (g) 250 218 218 218 SMGCC1 (g) 39 SMGCC2 (g) 48 SMGCC3(g) 51 Reduction of TiO₂ (% weight) 0 12.8 12.8 12.8 PVC (%) 21 21 21 21Properties on application of the paint formulation Contrast ratio at 7.5m²/l spreading rate (%) 98.6 98.5 98.6 98.5 Gloss obtained using acoater gap of 150 μm 20° 51.8 50.6 50.6 55.7 60° 80.3 79.7 79.7 81.7 85°93.6 95.9 96.2 96.8 Gloss obtained using a coater gap of 300 μm 20° 55.652.4 54.7 56.8 60° 79.4 78.7 80.1 80.5 85° 95.6 95.7 96.5 95.8

The results of the above table show that replacing a part of TiO₂ withthe SMGCC according to the invention, and having d₉₈/d₅₀ values rangingfrom 2.4 to 5, results in coatings having essentially the same opacity(contrast ratio) as the comparison formulation having equal PVC but onlyTiO₂. Gloss values are observed to be equivalent or improved relative tothe comparison formulation having equal PVC but only TiO₂.

The invention claimed is:
 1. Concrete, wood, paper, metal or boardcoated with a glossing and opacifying coating composition comprising:(i) at least one submicron ground natural calcium carbonate (SMGCC)having a volume median particle diameter d₅₀ of 0.05 to 0.3 μm and a d₉₈of less than or equal to 0.6 μm, and titanium dioxide, wherein thetitanium dioxide:SMGCC weight ratio in the composition is from 75:25 to98:2, and wherein the calcium carbonate is calcite, marble, chalk orlimestone; and (ii) glossing and opacifying coating compositioncomponents, wherein the glossing and opacifying coating composition hasa pigment volume concentration (PVC) of from 5 vol.-% up to a criticalpigment volume concentration (CPVC), and wherein the glossing andopacifying coating composition, applied to a contrast card to form alayer having a thickness of 150 μm or 300 μm, has a gloss that is within±3% of the gloss of the same composition and thickness in which theSMGCC is fully replaced with the titanium dioxide, when gloss ismeasured either at a 60° or an 85° incident angle according to DIN67530.
 2. The concrete, wood, paper, metal or board according to claim1, wherein the glossing and opacifying coating composition has a PVC offrom 10 to 30 vol.-%.
 3. The concrete, wood, paper, metal or boardaccording to claim 1, wherein the glossing and opacifying coatingcomposition has a PVC of from 15 to 25 vol.-%.
 4. The concrete, wood,paper, metal or board according to claim 1, wherein the glossing andopacifying coating composition has a PVC of from 17 to 21 vol.-%.
 5. Theconcrete, wood, paper, metal or board according to claim 1, wherein theSMGCC has a volume median diameter d₅₀ of 0.08 to 0.3 μm.
 6. Theconcrete, wood, paper, metal or board according to claim 1, wherein theSMGCC has a volume median diameter d₅₀ of 0.1 to 0.2 μm.
 7. Theconcrete, wood, paper, metal or board according to claim 1, wherein theSMGCC has a d₉₈/d₅₀ of greater than
 3. 8. The concrete, wood, paper,metal or board according to claim 1, wherein the SMGCC has a d₉₈ of lessthan or equal to 0.4 μm.
 9. The concrete, wood, paper, metal or boardaccording to claim 1, wherein the titanium dioxide:SMGCC weight ratio isfrom 75:25 to 90:10.
 10. The concrete, wood, paper, metal or boardaccording to claim 1, wherein the titanium dioxide:SMGCC weight ratio isfrom 80:20 to 85:15.
 11. The concrete, wood, paper, metal or boardaccording to claim 1, wherein the glossing and opacifying coatingcomposition components are selected from the group consisting of one ormore of a resin, a binder, a pigment, a defoamer, a levelling agent, aflatting agent, a preservative, an optical brightener, a lightstabilizer, a reheological additive, a thickener, a dispersant, asolvent, a filler, an anti-settling agent, a surfactant, a metal, and aUV absorber.